Machine for the coating of webs of paper and like absorbent material



Jan. 30, 1945. A. R. TRIST 2,368,176

MACHINE FOR THE COATING 0F WEBS OF PAPER AND LIKE ABSORBENT MATERIALFiled Sept. 17, 1941 5 Sheets-Sheet l INVENTOFQI an. A -r'j Jan 30,1945. TRlsT 2,368,176

. MACHINE FOR THE COATING OF WEBS OF PAPER AND LIKE ABSORBENT MATERIALFiled Sept. 17, 1941 5 Sheets-Sheet 2 Jan. 30, 1945. R TRlsT 2,368,176

MACHINE FOR THE COATING OF WEBS OF PAPER AND LIKE ABSORBENT MATERIALFiled Sept. 17, 1941 5 Sheets-Sheet 3 Wham-1945 ascents MACHINE FOR THECOATING F WEBB OF PAPER AND LIKE ABSOBBENT MATERIAL Arthur RonaJdTrlat,London, England Application September 11, 1941, Serial No. 411,1 rn-omiiii-min September- 20, 1940 a 4 Claims. (01. 91-43) This inventionrelates to improvements in ma! chines for the coating of webs-of paperand like absorbent material and has for its object to effect suchcoating continuously and evenly |by a-simple machine capable ofoperation at an economically high speed and which can be adjusted easilyto control the width and thickness of the coating, bearing in mind theviscosity of the coating mixture. I

The invention is particularly useful for the application to a web ofpaper of a mixture which will not water wet the paper, for example anoil phase resin bearing emulsion. I

The invention consists in a machine for the coating of webs of paper andlike absorbent material comprising a moving bed for supporting said web,means for applying coating mixture to said web without water wettingsaid web and stationary scraper means cooperating yieldingly with thecoated surface of the web to spread the coating mixture and produceathin and even coating.

The invention may be-carried into effect-in a variety of ways and bydivers mechanical. constructions, that is to say, the elastic bed may bein the form of a roller or a continuous belt and, if the latter, partsthereof .may be inclined at different angles or the belt as a whole maybe tilted; the emulsion can 'be supplied by gravity, by immersion, or bysurface contact, and the elastic cooperation can be adjusted andcontrolled in different ways.

In the accompanyin drawings I Figure 1 shows diagrammatically one formof roller machine in which the emulsion is fed by gravity from a ductsupplied by pressure feed; V Figure 2 is a erspective' fragmentarysection through a part of a machine of the kind shown in Figure l; vFigure 3 shows diagrammatically a different form of roller machine inwhich the emulsion is applied by surface contact;

Figure 4 shows diagrammatically a form of belt machine for applyingsuccessive coatings, in which the emulsion is fed by gravity from ductsor fountains supplied by pressure feed;

Figure 5 show diagrammatically an arrangement for applying successivecoatings in which there is provision forc nsiderable drying time betweenthe coats;

Figure 6 shows diagrammatically an arrangement for applying coatingssuccessively to both sides of a Web;

Figure 7 *is a fragmentary view showing as a in Figure 3 withitsmounting and adjusting Figure 8 is a fragmentary view showing ,as adetail a difierent kind of scraper blade suitable for use in Figures 1and 2 with its mounting and adjusting means. 1

This invention most conveniently makes use of an emulsion as the vehiclefor thecoating sub! stance (pigment and binder for example) whichemulsion comprises a continuous phase consisting of a l'iyclrocarbon(such as a petroleum for example) a disperse phase consisting of waterin a finely divided state, and the usual emulsifying and phasecontrolling agents producing appropriate protective colloids allcompounded to produce a mixture of the required viscosity suitable forhydraulic feed to the fountains and. ducts of the various arrangementsdescribed hereinafter;

Emulsions of this kind are not volatile in the ordinary sense of theword-but when such an emulsion is applied to an absorbent material (suchas paper for example) it depositsth'e' pigment and other substances (ifany) on the-absorbent material without water wetting such material andthereby. reducing its tensile strength and effects such deposition .veryrapidly so that surface treatment of the coating or of theweb aftercoating has to be eifected as quickly as possible. v i i As shown inFigures 1 and 2 the improved coat ing means consistsof a roller a ofmaterial, the resilience of which has to be regarded as supplementary tothe resilience-of the web supported thereby so that when the web isthick the material may be com'parativelyinelastic, but with ordinarythin paper webs, the material selected is elastic (such asindia rubber,for example), which is journalled at b and a-stationary trailing scraperblade 0 angularly arranged relatively to the surface of the roller a soas to form'a duct or fountain d, the width of which'is determined bymarginal restrictors, side walls or dykes (here; inafter called dykes)e, mounted on the blade 0 in an adjustable manner to" form-a trough ofdefinite width for-the'coatin'g e'mulsion'f.

The dykes e may be mounted on a stationary part of the machine or on thestock carrying the scraper blade 0 instead of on the" scraper bladeitself as may be found to be convenient as a matter ofconstruction'or'operation.

As shown in Figure lthe web gof paper or'th like passes from the stock-roll 'h around the roller b to be rewound on the' jroll 7', the web 9in its passage formingi-a boundary surface of the detail one kind ofscraper blade suitable for use duct or fountain'd,so" that the emulsion"I therein is applied to a defined part of the width of the web a for adefined period of time. The web a then passes between the surface of theroller b and the edge of the scraper blade so that the surplus depositis removed and that remaining as well as the surface of the web a issmoothed to produce a very even texture which may have the barestminimum of deposit thereon, the edge of the scraper blade c beingsmoothed toavoid any scratching or abrasion of the finished surface.

The coating operation is closely analogous to that of spreadin butter ona slice of bread with a knife and to obtain the best results for acertain thickness of the butter spread, the angle of the knife, thetorque exerted by the wrist, the resilience of the bread and theviscosity of the butter, all have to be coordinated, similarly in thepresent invention, the angle of the scraper blade 0, the contactpressure, the resilience of the elastic roller b and the viscosity ofthe emulsion, all have to be adjusted to cooperate with the particularweb being coated if a coating of even thickness is to be obtained.

As shown in Figure 3, the emulsion f is supplied to a tank 1 locatedbeneath the roller a, iournalled at b, and the dykes e are arranged inthe tank I on the underside of the roller :1 to limit the width to whichthe emulsion is applied to the web a, whilst the surplus deposit fromthe emulsion is removed by the trailing stationary scraper blade 0 whichis adjusted to produce the required smooth and even texture on thecoated surface of the web 0.

In the arrangement shown in Figure 4, a belt a of elastic material (suchas India rubber reinforced with textile material for example) issubstituted for the roller a and its resilience has to comply with thesame requirements as that of the roller a, said belt a being supportedon rollers m or in any other convenient way. A fountain or duct forcontaining the emulsion I (supplied to said fountain under pressure) isformed by the stationary scraper blade c and a wall 1 the width of thefountain or duct being defined by dykes e which can be listed sidewaysas desired within the dimensional limits of the construction.

In all cases the scraper blade c is mounted on a stock n and may consistof a single blade, which may be stiff or somewhat elastic, of stainlesssteel for example, secured in place by screws n as shown in Figure 7 orof several blades ccc forming a laminated structure as shown in Figure8.

The stock n may be clamped to hold the scraper assaivo blade 0 at therequired angle to and with the requisite pressure on the resilientsurface of the elastic roller a to get the spreading action hereinbeforereferred to but in some cases parts of the stock n may be mounted on aspindle o carrying a lever 12 connected to one end of a spring (I. theother end of which is anchored to a stationary part of the .machlnestructure, so that the spring q tends to move the edge of the scraperblade 0 away from the periphery of the roller a, and to provide a screw7: to force the edge of the scraper blade c towards the periphery of thedifferent coating mixtures, different pressures will have to be appliedto obtain a coating of the required thickness.

In the arrangement shown in Figure 8. the edge of the scraper blade c isurged into contact with the surface of the roller a or belt a by aspring such as q and is restrained by a stop screw such as k, the partsa and I: being suitably anchored and mounted.

The actual construction of the roller a forms no part of this inventionbut it may be hollow, that is to say, in the form of a drum at having anelastic sheathing a of India rubber or other material, substantiallyunaffected by the emulsion and the operation of the machine in apractical way, of a consistency and thickness to provide the essentialresilience of the roller and the web to give the required yieldingcooperation with the scraper blade c.

As the web a is not water wetted by the applied emulsion its tensilestrength (if of paper) is not materially affected, so that power may beapplied to the rewind roll 1 sufiicient to operate the machine, butusually the roller a or belt a will be urged to relieve the stress inthe web 9 and the stock rollit may have some power applied thereto.

Generally, it is necessary to apply more than one coating of emulsion toa given web a and to enable this to be done in a single operation, two,three, four, five, six or more hoppers each having a stationary scraperblade c mounted for exact adjustment, a wall 1 and dykes e may bearranged in succession as shown in Figure 4, the belt a being as long asrequired and being supported by rollers at the points of operation oralternatively, being air fioated on a fiat bed.

When a number of coatings have to be applied successively it may befound that the length of a machine as shown in Figure 4 is inconvenient,and in such case, the arrangement shown in Figure 5 should be used. Inthis arrangement use are rollers usually of elastic material, eccc arethe stationary trailing scraper blades which are arranged to act asfountains or ducts and receive pressure fed emulsion, h is the stockroll, I the rewind roll, and t are guide and jockey rollers fordeflecting the web a to follow the path shown.

' When both sides of a web a have to be coated this may be effectedeconomically and rapidly by an arrangement such as is shown in Figure 8in which there are two rollers a possessing the required resilience, andthe web a passes from the left hand roller a, thence between the rollersa upwardly to the roller t, downwardly to the roller t and then upwardlyaround the upper part of the right hand roller a, thence the web 0passes downwardly to the rewind roll a so that one surface of the web ais exposed on the left hand roller a and the other surface of the web ais exposed on the right hand roller :1 as shown.

A trailing stationary scraper blade c is applied conveniently to eachroller (1 to form two gutters dd which are fitted with dykes e as shownin Figure 6 so that as the web 0 passes from the roll it to the roll 1firstly a coating is applied to one side of the said web, smoothed andfinished by the cooperation of the blade and roller and then a coatingis applied to the other side of the said web, smoothed and finished inturn by the cooperation of the other blade and roller, the length of theweb between the points at which coating occurs being sufiiciently spacedto provide for P p 1 7 8- I claim:

1. A machine for coating absorbent continuous webs with a substancesuspended in an oil phase emulsion containingfinely divided water as thedisperse phase, said machine comprising a relatively resilient movablesupport in contact with one surface of said'web, means for supplying theemulsion to the moving surface of said web not in contact with saidsupport and a stationary blade means including a knife edge portion andmeans to urge said knife edge portion resiliently into contact with theemulsion coated surface of said supported moving web.

2. The machine claimed in claim 1, in which said blade is laminated.

3. A machine for coating absorbent continuous webs with a substancesuspended in an oil phase emulsion containing finely divided water asthe disperse phase, said machine comprising a rotatable roller with aperipheral layer of India rubber, the external surface of which is incontact with one surface of said web, means for supplying the emulsionto themoving surface of said web not in contact with said externalsurface of the peripheral layer of India. rubber, and a sta- 4 tionaryblade means including a knife edge porstationary blade supported so asto trail on the emulsion coated surface of said web whilst descending,spring means urging the free edge of said blade into yieldingco-operation with said peripheral layer of India rubber and marginalrestrictors mounted on said blade intermediate of its ends to form ahopper of substantially triangular transverse cross section for theemulsion.

ARTHUR RONALD 'r RIs'r.

